Physicochemical parameter charts for gases in fluid inclusions

Abstract

A great wealth of analytical data for fluid inclusions in minerals indicate that the major species of gases in fluid inclusions are H2O, CO2, CO, CH4, H2 and O2. Three basic chemical reactions are supposed to prevail in rock-forming and ore-forming fluids: $$\begin{gathered} H_2 + 1/2{\text{ O}}_{\text{2}} = H_2 O, \hfill \\ CO + 1/2{\text{ O}}_{\text{2}} = CO_2 , \hfill \\ CH_4 + 2{\text{O}}_{\text{2}} = CO_2 + 2H_2 O, \hfill \\ \end{gathered} $$ and equilibria are reached among them. $$\lg f_{O_2 } - T,{\text{ }}\lg f_{CO_2 } - T$$ and Eh-T charts for petrogenesis and minerogenesis in the supercritical state have been plotted under different pressures. On the basis of these charts $$f_{O^2 } ,{\text{ }}f_{CO_2 } $$ , Eh, equilibrium temperature and equilibrium pressure can be readily calculated. In this paper some examples are presented to show their successful application in the study of the ore-forming environments of ore deposits.